1. Field of the Invention
Methods and apparatuses consistent with the present invention relate to transmitting a message to a plurality of wireless devices that are classified into groups.
2. Description of the Related Art
Wireless devices in a wireless home network wirelessly transmit messages. Accordingly, wireless devices or access points (AP) using the same channel can receive messages from one another. Sometimes, however, a wireless device needs to transmit a message to only a specific wireless device.
The Institute of Electrical and Electronics Engineers (IEEE) 802.11i standard defines various message security methods. In particular, according to the Wi-Fi Protected Access-Pre-Shared Key (WPA-PSK) standard, which is a version of the IEEE 802.11i standard for home networks or small office/home office (SOHO) environments, when a wireless device communicates one-on-one with an AP using a unicast method, messages transmitted between the wireless device and the AP can be encrypted with a pairwise key which is shared only between the wireless device and the AP. In order to transmit a message to a plurality of wireless devices, the message may be encrypted with a group key corresponding to a group into which the plurality of wireless devices are classified.
FIG. 1 is a diagram illustrating a related art method of unicasting a message encrypted according to the IEEE 802.11i standard. Referring to FIG. 1, a first wireless device 11 encrypts a message with a first pairwise key PK1 and transmits the message encrypted with the first pairwise key PK1 to an AP 1. The AP 1 receives the message encrypted with the first pairwise key PK1 from the first wireless device 11 and decrypts the received message with the first pairwise key PK1, thereby restoring the original message. The AP 1 encrypts the restored message with a second pairwise key PK2 and transmits the message encrypted with the second pairwise key PK2 to a second wireless device 12. The second wireless device 12 which holds the second pairwise key PK2 can decrypt the message encrypted with the second pairwise key PK2. Wireless devices which do not hold the second pairwise key PK2 cannot decrypt a message encrypted with the second pairwise key PK2 even if they receive a message encrypted with the second pairwise key PK2.
FIG. 2 is a diagram illustrating a related art method of multicasting a message encrypted according to the IEEE 802.11i standard. Referring to FIG. 2, a first wireless device 21 encrypts a message with a group key GK allocated to a group to which the first wireless device 21 belongs, and transmits the message encrypted with the group key GK to an AP 2. The AP 2 receives the message encrypted with the group key GK from the first wireless device 21 and transmits the received message as it is. Then any wireless device that holds the group key GK can decrypt the message transmitted by the AP 2, whereas wireless devices that do not hold the group key GK cannot decrypt the message transmitted by the AP 2.
Recently, wireless home networks are becoming more widespread due to their reduced costs and higher speeds. Wireless devices can be readily connected to wireless home networks without additional installation operations, and thus, wireless home networks are expected to be commonplace in home networking in the near future. However, wireless devices which are unknown to a user of a wireless home network can be connected to the wireless home network of the user. In particular, in a Universal Plug and Play (UPnP)-based wireless home network environment, a wireless device which is unknown to a user may find a wireless device of the user and control the detected wireless device without authorization from the user.
According to the IEEE 802.11i standard, the encryption of messages is conducted on a data link layer. However, according to the UPnP standard, the detection of a wireless device is conducted on an application layer. Therefore, related art IEEE 802.11i-based methods of encrypting messages cannot prevent a wireless device which is unknown to a user from finding a wireless device of the user in a UPnP-based wireless home network environment and controlling the detected wireless device without authorization from the user.